This application addresses broad Challenge Area (06): Enabling Technologies, and specific Challenge Topic, 06-AA-108: Innovative Technologies for Drinking Pattern Analysis. Using an innovative technique to assess drinking patterns (oral assays), the purpose of this application is to examine the club as a specific ecological context to assess drinking patterns and related risky behaviors. The club setting attracts young adults who are working and not in college (approximately one-third of attendees are in college) and thus allows us to measure drinking patterns at high-risk ecological moments for young adults in hard to reach young adults. The specific aims are: (1) To determine the contribution and interaction of personal and group characteristics on drinking and patterns at entrance and exit (as measured by biological assays), both in the presence and absence of other substances. Drinking patterns are defined as amount of alcohol consumed at entrance/exit (measured by biological assays), intentions to drink in the club, and perceived level of intoxication at entrance/exit. Personal characteristics include demographics, lifetime and recent history of drug use, usual drinking patterns, and regularity of club attendance. Group characteristics include composition of group, group drinking patterns, group drug use patterns, and designated driver in group. (2) To determine the accuracy of self-reports of drinking patterns at exit, relative to biological assays of alcohol use at exit, and examine the extent to which concomitant drug use, individual and group characteristics relate to this accuracy. (3)To identify the extent that individual drinking intentions, as measured on entry, accurately predict exit drinking patterns, and the extent to which concomitant drug use, individual and group characteristics, relate to this accuracy. Using portal methodology, we will be randomly sampling groups of patrons as they approach the club and collecting data anonymously as they enter and exit the club. By sampling multiple high attendance evenings (Thursday, Friday, Saturday) over the course of 12 months in clubs, we will be able to include sufficient numbers of groups (N=360) from various contexts with an estimated N of 864 individuals. By collecting information from the group, data can be analyzed to determine how groups influence the drinking patterns over the course of the evening for young adults who frequent clubs. These findings will provide a framework for developing environmental strategies to reduce alcohol use in the club settings. In addition, this study will provide us with valuable data about group behaviors that will serve as a basis for developing a brief prevention strategy for groups attending clubs.